1. Field of the Invention
The present invention relates to a heat treatment method and a heat treatment apparatus for substrate heating, and more particularly to a heat treatment method and a heat treatment apparatus that allow a substrate to be heated to the desired temperature at a high rate and with good uniformity.
2. Description of the Related Art
As wafers have increased in diameter due to the need to achieve higher semiconductor integration and lower manufacturing costs, it has become difficult to form films with high precision across the surfaces of all the wafers of a batch inside a conventional batch-type vertical CVD apparatus. In view of this, single or dual substrate processing CVD apparatus in which each wafer is individually treated are being mostly used at the moment. A single or dual substrate processing CVD apparatus may be a cold-wall type or a hot-wall type.
(1) Cold-Wall Type
In a cold-wall apparatus, a wafer placed in a cooled reactor furnace body is directly heated by a lamp, or the wafer is heated after being placed on a susceptor heated by a heater, a lamp, or the like, and a film is deposited by feed a starting material gas. This type of apparatus differs from the batch type in that fluctuations among wafers can be reduced because the film can be deposited under the same heating conditions each time, but the wafers must be rotated in order to obtain a uniform film thickness distribution across the water surface, or various measures must be taken in order to create uniform conditions in which gas is fed above the wafers through a shower plate. Another approach is to render the wafer temperature uniform by adjusting the shape or arrangement of heating lamps, as described in Japanese Unexamined Patent Application (Kokai) 4-255214.
(2) Hot-wall Type
In a hot-wall apparatus, on the other hand, it is possible to dispense with complicated means for creating uniformity such as those found in cold-wall CVD apparatus, and the wafer temperature can be readily rendered uniform in the manner disclosed, for example, in Japanese Unexamined Patent Application 7-94419. FIG. 10 is a schematic cross section of such a hot-wall CVD apparatus. A reactor furnace body 3 itself is heated by resistance heater 4 disposed outside the reactor furnace body 3, and wafers W inside the reactor furnace body 3 are heated. A wafer W supported by tweezers 8 and transported from a transfer chamber 1 into the reactor furnace body 3 through a gate valve 5 is heated at a fairly high rate in the initial period of heating because or the temperature difference (400 to 700xc2x0 C.) with the hot-wall system, but because the heat-up rate is proportional to the fourth power of the temperature difference, the heat-up rate decreases as the wafer temperature approaches the temperature of the hot-wall system, and ultimately a period or 5 minutes or greater is required for preheating, as shown in FIG. 11. By contrast, lamp heating markedly reduces the preheating time without appreciably lowering the heat-up rate due to the fact that because the filament temperature is high (2500 to 3000 K), the difference in temperature between the water and the filament is about 2000xc2x0 C. even as the wafer approaches the desired temperature (400 to 700xc2x0 C.).
As referred to herein, xe2x80x9cpreheating timexe2x80x9d is the time elapsed between the moment a wafer W has been transferred to the reactor furnace body 3 and the moment the wafer W has reached the desired temperature and the desired uniformity has been achieved. The aforementioned hot-wall system is a system heated by a resistance heater 4 and composed of the reactor furnace body 3 itself and the atmosphere and objects inside the reactor furnace body 3.
A distinctive feature of the aforementioned hot-wall CVD apparatus is that because the wafer W and the interior walls of the reactor furnace body 3 are in a state of thermal equilibrium in which the temperatures of the two are equal to each other, the wafer temperature can be kept constant irrespective of the film type, providing excellent temperature uniformity and temperature stability. Another distinctive feature is that an additional gas introduction port (not shown) and an additional gas exhaust port (not shown) are provided at positions facing a CVD gas introduction port 6 connected to a flange 13 and an exhaust port 7 connected to a flange 14 across the wafers W, and a highly uniform film thickness is achieved by switching these ports during film formation and reversing the direction of gas flow.
Hot-wall CVD apparatus are disadvantageous, however, in that their throughput is low because the temperature of the wafers W is close to room temperature, and considerable preheating time which is about 5 minutes or longer (see FIG. 11) elapses between the moment the wafers are introduced into the reactor furnace body 3 and the moment the desired temperature is reached, resulting in an extended overall treatment time (tact time), including the film forming time.
In addition, this phenomenon becomes more pronounced with lower heating temperatures (furnace body temperatures). This occurs for the following reasons.
The lower the temperature (under about 500xc2x0 C.) of the reactor furnace body 3, the lower the spectral radiant intensity (radiation intensity) and the farther the shift of the blackbody radiation wavelength distribution (radiation wavelength distribution) toward longer wavelengths, as shown in FIG. 12. A silicon wafer, on the other hand, has a very low absorption coefficient at wavelengths longer than 1.2 xcexcm, resulting in poor heating efficiency and minimal absorption of heat from the example, the absorption efficiency is 3% and 15% at a wafer temperature of 400xc2x0 C. and 500xc2x0 C., respectively. Consequently, the heating efficiency decreases with a reduction in the temperature of the reactor furnace body 3. This causes considerable time to be expended when wafers are heated in a hot-wall CVD apparatus.
In addition, the temperature of the furnace body itself decreases due to the introduction of cold wafers W into the reactor furnace body, and time is needed for this temperature to recover. A feed-forward control (FFC) technique and a rapid heating technique have been proposed as means aimed at addressing this problem.
(1) FFC Technique
As noted above, the hot-wall system, in addition to being disadvantageous in the sense that the wafer heat-up rate is slow, is also disadvantageous in the sense that the temperature of the system is lowered by the introduction of wafers into the system. FFC is a technique in which the second drawback is dealt with by presetting the temperature of the system somewhat higher in view of the reduction in the temperature of the reaction furnace body. According to FFC results, however, setting the system temperature (FFC set temperature) somewhat higher (in the absence of a cooling means, the temperature cannot be set high, and it is no more than several tens of degrees Centigrade) merely improves the preheating time somewhat, failing to produce a depreciable reduction, as shown in FIG. 14.
(2) Rapid Heating Technique
As shown by the schematic cross section in FIG. 15, the technique envisages providing a rapid heater 9 in which the heat capacity of the heater for heating a reactor furnace body 3 is reduced to allow for rapid heating, and installing a forced air cooling mechanism (not shown) in which cooling air is forced through an excessively heated reactor furnace body 3 to allow the reactor furnace body 3 to be cooled at a high rate. According to this technique, the system temperature (FFC set temperature) during the loading of a wafer W can be set higher, making it possible to reduce the initial heating time needed to achieve the set temperature, as shown in FIG. 16. It is still impossible, however, to reduce the control period that needs to elapse before the set temperature can be stably sustained, so the resulting effect is small despite a reduction in the preheating time in comparison with conventional practice. Rather, this rapid heating technique aims at adequately recovering the temperature of the system to the FFC set temperature in the period between the end of film formation and the introduction of the next wafer. The hot-wall system was originally created to counter the effect of a disturbance such as the introduction of wafers W, and to maintain constant temperature in a sustained manner. Raising or lowering the temperature of the system as such in order to achieve a certain reduction in the heating time in the manner envisaged by the rapid heating technique is unsuitable because it negates the inherent advantages of the hot-wall system and complicates wafer temperature control.
As noted above, a distinctive feature of hot-wall reactor furnace body heating is that the wafer W and the furnace body 3 can be kept at the same temperature if the wafer W is introduced into the uniformly heated furnace body 3 and a thermal equilibrium is established, and that there is no need to take into account the effect of the different types of wafer W on the emissivity, absorption coefficient, and other thermal characteristics.
The above distinctive feature, however, is based on an ideal system in which the heat capacity of the hot-wall reactor furnace body 3 is infinitely large in relation to the heat capacity of the wafer W, whereas in reality a cold wafer W disrupts the system into which it is loaded, causing the temperature of the entire system to decrease.
The present invention provides a heat treatment method and a heat treatment apparatus that can be realized in a more ideal form. Specifically, an object of the prevent invention is to provide a heat treatment method and a heat treatment apparatus in which the advantages of commonly used hot-wall heat treatment apparatus can be preserved such that a uniform substrate temperature can be easily obtained, in which the unacceptably long substrate heating time of conventional hot-wall heat treatment apparatus can be reduced, and in which equipment throughput can be enhanced.
A distinctive feature of the present invention is the combined use of lamp (non-equilibrium) heating and hot-wall furnace body (equilibrium) heating. Hardly any disruption is caused in a system if a substrate is loaded into the system after the substrate W is brought in advance to the same average temperature as the system before the substrate is loaded into the system, or if the substrate is heated vary rapidly from the outside in such a way that the substrate is brought to the same temperature as the system before a substantial amount of heat is taken from the system immediately after substrata loading. The temperature of the substrate W can be subsequently rendered uniform in a comparatively short time by the inherent heat transfer capabilities of the substrate. In the process, lamp heating is used to heat the substrate to the same temperature as the system, and hot-wall furnace body heating is used to establish a uniform substrate temperature thereafter. To reiterate, a significant feature of lamp heating is that the heating time of a substrate can be readily reduced (the heating rate is proportional to the fourth power of the temperature difference and to the first power of radiant intensity) by creating a large difference in temperature between the light emitter (the filament inside a lamp) and the substrate (the object being heated), and raising the radiant intensity of the light emitter. With the products currently available on the market, lamp heating can yield a heat-up rate of about 100xc2x0 C. per second. Consequently, the use of lamp heating can accelerate the process several tenfold, as compared with the five minutes needed to heat a substrate to 500xc2x0 C. with hot walls.
Lamp heating is seriously disadvantageous, however, in that the continuously non-equilibrium character of such heating (in this case, the temperature of the substrate is determined by the balance between the heat quantity emitted by the radiation from the lamp and received by the substrate, and the heat quantity emitted by the radiation from the substrate) makes it very difficult to maintain a constant temperature, and that it is impossible to obtain a uniform temperature across a substrate surface unless the illuminance distribution of the substrate is controlled with high accuracy.
In view of this, the present invention is aimed at providing a heat treatment method and a heat treatment apparatus in which lamp (non-equilibrium) heating and hot-wall furnace body (equilibrium) heating are used together, substrates are rapidly heated (in this case, nonuniformly) by lamps at the start of heating under conditions in which the temperature distribution is largely ignored, and a uniform temperature is then established across the substrate surface by employing heat transfer in a thermally uniform system. Following is a description of the means employed to attain the above-described object of the present invention.
The invention of claim 1 resides in a heat treatment method wherein a hot-wall heat treatment apparatus in which the temperature inside a reactor furnace body is kept at a prescribed level with the aid of resistance heaters prior to substrate loading into the reactor furnace body is provided with lamps disposed outside the reactor furnace body and designed to heat substrates loaded into the reactor furnace body by light emission transmitted through the reactor furnace body, comprising a step in which the substrates are loaded into the reactor furnace body kept at the prescribed temperature, and the substrates are then directly heated to a desired temperature by the lamps provided outside the reactor furnace body under continued heating by the resistance heaters. The present invention allows high throughput and improved process productivity to be obtained because the heating time on be markedly reduced in comparison with the heating time based on the use of hot walls.
The invention of claim 2 resides in a heat treatment method as defined in claim 1, this heat treatment method comprising a step in which the substrates are heated to substantially the desired temperature by the lamps, the lamps are then switched off, azo the substrates are kept for a prescribed time inside the reactor furnace body kept at the prescribed temperature by the resistance heaters before a reaction treatment is started. It is preferable to use a procedure in which the lamps are switched off once the average temperature of the substrates has been brought to substantially the desired temperature by lamp heating, the substrates are kept for a prescribed time in the hot-wall system after the lamps have been switched off, and a state in which the substrates themselves have achieved a uniform state through heat transfer is awaited. It is thus possible to overcome one of the drawbacks of lamp heating; namely, that a substrate can be rapidly heated but it is difficult to keep at a constant temperature with high accuracy and in a controlled manner. The present invention allows the heating temperature to be controlled with higher accuracy than in the case of a heating temperature achieved with lamp heating.
The invention of claim 3 resides in a heat treatment method as defined in claim 1, this heat treatment method comprising presetting the temperature inside the reactor furnace body before the lamps are lighted to a level different from the a desired reaction temperature in such a way that the temperature inside the reactor furnace body coincides with the desired reaction temperature when the lamps are switched off after the substrates have been heated to substantially the desired temperature by the lamps. The temperature of the hot-well system in preset to a level somewhat higher or lower than the treatment temperature to compensate for variations in the hot-wall system, such as temperature reductions during substrate transport or the heating of the reactor furnace by the long-wavelength components of lamp light during lamp heating. Setting the temperature inside the reactor furnace body to a level different from the reaction temperature prior to lamp lighting makes it possible to keep the temperature inside the reactor furnace body at the desired reaction temperature when the lamps are switched off.
The invention of claim 4 resides in a heat treatment method as defined in claim 1, this heat treatment method comprising: measuring in advance the lamp output, lamp lighting time, and other lamp heating conditions needed for the substrate temperature to substantially achieve a prescribed level after the substrates (dummy substrates) have been loaded into the reactor furnace body and the lamps lighted; and heating the substrates(substrates for products) in the actual substrate treatment step under the lamp heating conditions obtained as a result of the measurements. An optimum heating condition suitable for rapid heating can be obtained because the optimum lamp output and lighting time are measured in advance by using the dummy substrates having substantially the same thermal characteristic as that of the substrates for products. The optimum lamp output and lighting time are lamp output and lighting time which needed to achieve a prescribed temperature when the dummy substrates are heated under substantially the same lamp heating conditions as those that are to be established during an actual substrate treatment.
The invention of claim 5 resides in a hot-wall heat treatment method comprising keeping the temperature inside a reactor furnace body at a prescribed level with the aid of resistance heaters prior to substrate loading into the reactor furnace body, this heat treatment method further comprising a stop in which the substrates are preheated in such a way that the substrate temperature prior to substrate loading into the reactor furnace body is higher than the prescribed temperature inside the reactor furnace body. This method comprises providing substrate preheater designed to preheat the substrates and disposed in a transfer chamber connected to the reactor furnace body, estimating the reduction in substrate temperature during the loading of the substrates from the transfer chamber into the reactor furnace body kept at the prescribed temperature, and preheating the substrates to an excess commensurate with the temperature reduction in such a way that the substrates are kept at the desired temperature immediately after being loaded into the reactor furnace body.
Although the present invention entails providing the transfer chamber with additional substrate preheater or requiring that the substrates be heated for a longer time before being loaded into the reactor furnace body, the fact that the substrates are preheated outside the reactor furnace body instead of inside the reactor furnace body makes it possible to reduce the thermal effect on the reactor furnace body and to utilize the hot-wall feature. In addition, the reactor furnace body does not need to be transparent, so the arrangement is not limited to apparatus for forming specific types of transparent films and can be applied to a heat treatment apparatus capable of handling any type of film.
The invention of claim 6 resides in a heat treatment method as defined in claim 5, this heat treatment method comprising: measuring the substrate cooling rate in advance and calculating on the basis thereof an appropriate excess temperature representing the difference between the prescribed temperature inside the reactor furnace body and the preheating temperature of the substrates; and preheating the substrates in the actual treatment step on the basis of the appropriate substrate preheating temperature determined based on the excess temperature calculated using the measurements. Calculating a more appropriate excess temperature allows the substrates to be preheated to the optimum temperature, making it possible to minimize the thermal effect inside the reactor furnace body brought about by the loading of the substrates into the reactor furnace body, and hence to further reduce the time needed to stabilize the substrate temperature after the substrates have been loaded into the reactor furnace body.
The invention of claim 7 resides in a heat treatment method as defined in claim 5, this heat treatment method comprising estimating the different reductions in temperature during transport due to the differences in the distance of two substrates between their respective preheating positions and the reactor furnace body when these substrates are simultaneously preheated and loaded into the reactor furnace body, and independently preheating each substrate under a respective set of desired preheating conditions. Because two substrates are independently preheated at the same time, it is possible to estimate the difference in transport time due to the difference between the distances over which the substrates are transported from their respective preheating positions to the reactor furnace body. In other words, the difference in the temperature reduction between the substrates can be estimated, and each substrate can be preheated under its own set of desirable heating conditions.
The invention of claim 8 resides in a hot-wall heat treatment apparatus for heating the interior of a reactor furnace body with the aid of resistance heaters provided outside the reactor furnace body, this heat treatment apparatus comprising: lamps provided outside the reactor furnace body and designed to heat substrates inside the reactor furnace body by light emission transmitted through the reactor furnace body; resistance heater controller that energizes the resistance heaters prior to substrate loading into the reactor furnace body, keeps the temperature inside the reactor furnace body at a prescribed level, and maintains this energized state after the substrate have been loaded into the reactor furnace body; and lamp controller that lights the lamps after the substrates have been loaded into the reactor furnace body, heats the substrates to a near-prescribed temperature, and switches off the lamps following heating. The reactor furnace should preferably be a single or dual substrate processing furnace made of quartz and designed to treat approximately one or two substrates at a time. The lamps should preferably be halogen lamps. The resistance heater control unit and lamp control unit may be configured separately or integrally.
Lamps and resistance heaters are provided outside the reactor furnace body, and lamp (non-equilibrium) heating and hot-wall (equilibrium) heating are used jointly. First, the reactor furnace body is kept at a prescribed temperature by resistance heating prior to substrate loading. Next, after the substrates have been loaded into the reactor furnace body, the substrates are rapidly heated by the lamps to a near-prescribed temperature, and the lamps are switched off. The substrate temperature is subsequently rendered uniform by utilizing the heat transfer of the substrate in the system where a uniform thermal state has been established through hot-wall heating. Because a uniform substrate temperature is established by keeping the reactor furnace body at a prescribed temperature, there in no need to maintain particularly high accuracy when controlling the distribution of illuminance across the substrates during lamp heating. The present invention yields a high-throughput heat treatment apparatus because the heating time is much shorter than when hot walls alone are used, and allows the heating temperature to be controlled with higher accuracy than when lamp heating alone is used.
The invention of claim 9 resides in a heat treatment apparatus as defined in claim 8, this heat treatment apparatus comprising performing a treatment while supporting the flat surfaces of the substrates substantially parallel to the direction of substrate transport inside the reactor furnace body. Because the substrates are supported inside the reactor furnace in such a way that the flat surfaces of the substrates are substantially parallel to the direction of substrate transport higher heating efficiency can be achieved through lamp heating and the substrates can be heated at a higher rate than when the substrates are supported such that their flat surfaces are perpendicular to the transport direction.
The invention of claim 10 resides in a heat treatment apparatus as defined in claim 9, this heat treatment apparatus comprising treating a single substrate or two substrates stacked in the vertical direction perpendicular to the flat surfaces of the substrates. A single or dual substrate processing heat treatment apparatus containing heating system capable of treating one or two substrates in which resistance heating and lamp heating are combined is thus adopted, making it possible to heat each substrate at a high rate and to heat-treat the entire substrates with high accuracy of the temperature and uniformity.
The invention of claim 11 is a heat treatment apparatus as defined in claim 9, this heat treatment apparatus comprising disposing the lamps opposite the flat surfaces of the substrates. Disposing the lamps opposite the flat surfaces of the substrates makes it easier for the light emitted from the lamps to effectively irradiate the flat surfaces of the substrates in comparison with an arrangement in which, for example, the lamps are disposed opposite the end faces of the substrates, it is therefore possible to heat the substrates at an even faster rate and to achieve even higher throughput.
The invention of claim 12 resides in a heat treatment apparatus as defined in claim 10 for treating two substrates, this heat treatment apparatus comprising an arrangement in which the lamps are provided at an upper position and a lower position, the flat surface of the upper substrate is directly heated by placing the upper lamps opposite the flat surface of the upper substrate, and the flat surface of the lower substrate is directly heated by placing the lower lamps opposite the flat surface of the lower substrate. Placing the upper lamps opposite the upper substrate, and the lower lamps opposite the lower substrate allows the upper substrate and lower substrate to be heated at a high rate by the upper lamps and lower lamps, respectively, making it possible to achieve an even greater increase in throughput.
In addition, adopting an arrangement in which the flat surface of the upper substrate is directly heated by the upper lamps, and the flat surface of the lower substrate is directly heated by the lower lamps makes it possible to heat the two substrates simultaneously and at a higher rate than when end faces of the substrates are heated. Furthermore, settings corresponding to different heating conditions can be selected for the upper lamps and lower lamps when the heating conditions of the upper substrate and lower substrate differ from each other. It is thus possible to provide a heating arrangement in which the temperatures of the upper substrate and lower substrate are rendered uniform.
The invention of claim 13 resides in a heat treatment apparatus as defined in claim 12, this heat treatment apparatus comprising substantially equalizing the distance between the upper lamps and the upper substrate with the distance between the lower lamps and the lower substrate. Substantially equalizing the distance between the upper lamps and the upper substrate with the distance between the lower lamps and the lower substrate facilitates uniform heating of the upper substrate and lower substrate and makes it possible to deposit uniform films on two substrates at the body time.
The invention of claim 14 resides in a heat treatment apparatus as defined in claim 8, this heat treatment apparatus comprising a plurality of the lamps arranged in the direction of substrate transport. Even when the heating conditions vary across the substrate surfaces, these substrate surfaces can be uniformly heated at a high rate because the settings for each lamp are selected in accordance with the heating conditions for this lamp.
The invention of claim 15 resides in a heat treatment apparatus as defined in claim 14, this heat treatment apparatus comprising using as the lamps rod-shaped lamps disposed perpendicular to the direction of substrate transport. It is important to provide an illuminance distribution that allows substrates to be uniformly heated by lamps. Strictly speaking, xe2x80x9cuniform substrate heatingxe2x80x9d and xe2x80x9cuniform illuminance distributionxe2x80x9d do not necessarily have the same meaning, and an optimum illuminance distribution does exist. Examples of methods used to control the illuminance distribution include those in which a plurality of lamps are appropriately arranged, those in which the emission density inside a rod-shaped lamp is adjusted, and those in which reflecting surfaces are provided. The simplest method is to use rod-shaped lamps and to arrange a plurality of these lamps perpendicular to the direction of substrate transport but parallel to the flat surfaces of horizontally held substrates. The average substrate temperature can thus be rapidly raised, and the temperature distribution across the substrate rendered uniform. As a result, the substrate temperature can be rapidly and uniformly raised to the desired level.
The invention of claim 16 resides in a heat treatment apparatus as defined in claim 12, this heat treatment apparatus allowing lamp output to be independently controlled. Lamp output can be independently controlled, making it possible to compensate for a temperature reduction brought about, for example, by the escape of heat through the areas adjacent to the transport port during transport. In addition, the film thickness distribution across a substrate surface can be arbitrarily corrected, the film thickness within a substrate surface can be rendered more uniform, and a film with highly accurate thickness and uniformity can be deposited across the entire surface. When different heating conditions are used for upper and lower substrates, the upper and lower lamps are controlled in accordance with these different heating conditions, making it possible to heat the upper and lower substrates in a uniform manner.
The invention of claim 17 resides in a heat treatment apparatus as defined in claim 8, this heat treatment apparatus comprising presetting the temperature inside the reactor furnace body before the lamps are lighted to a level different from a desired reaction temperature in such a way that the temperature inside the reactor furnace body coincides with the desired reaction temperature when the lamps are switched off. The temperature of the hot-wall system is preset to a level somewhat higher or lower than the treatment temperature to compensate for variations in the hot-wall system, such as temperature reductions during substrate transport or the heating of the reactor furnace by the long-wavelength components of lamp light during lamp heating.
The invention of claim 18 resides in a heat treatment apparatus as defined in claim 8, this heat treatment apparatus comprising: providing the reactor furnace body with detachable temperature sensor that measures the temperature in the vicinity of the substrates inside the reactor furnace body; using the temperature sensor disposed inside the reactor furnace body to measure in advance the lamp output, lamp lighting time, and other lamp heating conditions needed for the substrate temperature to substantially achieve a prescribed level after the substrates (dummy substrates) have been loaded into the reactor furnace body and the lamps lighted; and beating the substrates(substrates for products) under the lamp heating conditions obtained through these measurements in an actual substrate treatment step devoid of the temperature sensor. An optimum heating condition suitable for rapid heating can be obtained because the optimum lamp output and lighting time are measured in advance by using the dummy substrates having substantially the saw thermal characteristic as that of the substrates for products. The optimum lamp output and lighting time an lamp output and lighting time which needed to achieve a prescribed temperature when the dummy substrates are heated under substantially the same lamp heating conditions as those that are to be established during an actual substrate treatment.
The invention of claim 19 resides in a hot-wall heat treatment apparatus for keeping the temperature inside a reactor furnace body at a prescribed level with the aid of resistance heaters prior to substrate loading into the reactor furnace body, this heat treatment apparatus comprising: substrate preheater designed to preheat the substrates and disposed in a transfer chamber connected to the reactor furnace body; and preheating controller that preheats the substrates in such a way that the substrate temperature is higher than the proscribed temperature inside the reactor furnace body in order to compensate for the reduction in the substrate temperature when the substrates are loaded from the transfer chamber into the reactor furnace body kept at the prescribed temperature. More specifically, the preheating controller serves to estimate the reduction in temperature brought about when substrates are loaded into a reactor furnace body kept at a proscribed temperature, and to preheat the substrates to a higher temperature commensurate with the reduction in temperature such that the substrates have the desired temperature immediately after being loaded into the reactor furnace body. Although the transfer chamber is provided with additional substrate preheater, or the substrates must be heated for a longer time before being loaded into the reactor furnace body, the fact that the substrates are preheated outside the reactor furnace body instead of inside the reactor furnace body sags it possible to reduce the thermal effect on the reactor furnace body and to utilize the hot-wall feature. In addition, the arrangement is not limited to applications involving heat treatment apparatus for handling film through which lamp light transmits, and can be applied to a heat treatment apparatus capable of handling any type of file. Because the substrate preheater is provided in the transfer chamber, there is no need to provide special preheat chamber etc. Thus it is possible to miniaturizes the apparatus.
The invention of claim 20 resides in a heat treatment apparatus as defined in claim 19, this heat treatment apparatus comprising providing the transfer chamber with two preheating positions for allowing two substrates to be preheated at the same time; and two sets of substrate preheaters that allow the substrates disposed at the two preheating positions to be independently body preheated under the corresponding sets of desired heating conditions. Because two preheating positions and two sets of substrate preheaters are provided, and because two substrates are independently preheated at the same time, it is possible to estimate the difference in transport time due to the difference between the distances over which the substrates are transported from their respective preheating positions to the reactor furnace body. In other words, the difference in the temperature reduction between the substrates can be estimated, and each substrate can be preheated under its own set of desirable heating conditions.
The invention of claim 21 resides in a heat treatment apparatus as defined in claim 19, this heat treatment apparatus comprising providing the transfer chamber with temperature sensors for measuring the substrate temperature; heating the substrates in the transfer chamber with the aid of the substrate preheater; and computing the cooling rate of the substrates by measuring variations in the substrate temperature with the aid of the temperature sensors disposed in the transfer chamber, calculating on the basis thereof an appropriate excess temperature representing the difference between the prescribed temperature inside the reactor furnace body and the preheating temperature of the substrates, and establishing an appropriate substrate preheating temperature inside the transfer chamber. Calculating a more appropriate excess temperature allows the substrates to be preheated to the optimum temperature, making it possible to minimize the thermal effect inside the reactor furnace body brought about by the loading of the substrates into the reactor furnace body, and hence to further reduce the time needed to stabilize the substrate temperature after the substrates have been loaded into the reactor furnace body.
The invention of claim 22 resides in a heat treatment apparatus as defined in claim 19, this heat treatment apparatus comprising using lamps as the substrate preheater in the transfer chamber. The substrate preheater of the transfer chamber my be resistance heaters, but lamps are preferred from the standpoint of rapid heating.
The invention of claim 23 resides in a hot-wall heat treatment apparatus for heating the interior of a reactor furnace body with the aid of resistance heaters provided outside the reactor furnace body, this heat treatment apparatus comprising: lamps provided outside the reactor furnace body and designed to heat substrates inside the reactor furnace body by light emission transmitted through the reactor furnace body; resistance heater control means for energizing the resistance heaters prior to substrate loading into the reactor furnace body, keeping the temperature inside the reactor furnace body at a prescribed level, and maintaining this energized state after the substrate have been loaded into the reactor furnace body; and lamp control means for lighting the lamps after the substrates have been loaded into the reactor furnace body, heating the substrates to a near-prescribed temperature, and switching off the lamps following heating. The reactor furnace should preferably be a single or dual substrate processing furnace made of quartz and designed to treat approximately one or two substrates at a time. The lamps should preferably be halogen lamps. The resistance heater control unit and lamp control unit may be configured separately or integrally.
Lamps and resistance heaters are provided outside the reactor furnace body, and lamp (non-equilibrium) heating and hot-wall (equilibrium) heating are used jointly. First, the reactor furnace body is kept at a proscribed temperature by resistance heating prior to substrate loading. Next, after the substrates have been loaded into the reactor furnace body, the substrates are rapidly heated by the lamps to a near-prescribed temperature, and the lamps are switched off. The substrate temperature is subsequently rendered uniform by utilizing the heat transfer of the substrate in the system where a uniform thermal state has been established through hot-wall heating. Because a uniform substrate temperature is established by keeping the reactor furnace body at a prescribed temperature, there is no need to maintain particularly high accuracy when controlling the distribution of illuminance across the substrates during lamp heating. The present invention yields a high-throughput heat treatment apparatus because the heating time is much shorter than when hot wells alone are used, and allows the heating temperature to be controlled with higher accuracy than when lamp heating alone is used.
The invention of claim 24 resides in a hot-wall heat treatment apparatus for keeping the temperature inside a reactor furnace body at a prescribed level with the aid of resistance heaters prior to substrate loading into the reactor furnace body, this heat treatment apparatus comprising: substrate preheating means designed to preheat the substrates and disposed in a transfer chamber connected to the reactor furnace body; and preheating control means for preheating the substrates in such a way that the substrate temperature is higher than the prescribed temperature inside the reactor furnace body in order to compensate for the reduction in the substrate temperature when the substrates are loaded from the transfer chamber into the reactor furnace body kept at the prescribed temperature, more specifically, the preheating control means serves to estimate the reduction in temperature brought about when substrates are loaded into a reactor furnace body kept at a prescribed temperature, and to preheat the substrates to a higher temperature commensurate with the reduction in temperature such that the substrates have the desired temperature immediately after being loaded into the reactor furnace body. Although the transfer chamber is provided with additional substrate preheating means, or the substrates must be heated for a longer time before being loaded into the reactor furnace body, the fact that the substrates are preheated outside the reactor furnace body instead of inside the reactor furnace body makes it possible to reduce the thermal effect an the reactor furnace body and to utilize the hot-wall feature. In addition, the arrangement is not limited to application involving heat treatment apparatus for handling film through which lamp light transmits, and can be applied to a heat treatment apparatus capable of handling any type of film.